We get questions on this theme all the time. "How do I work out what age group to mention in my cover letter?" "Does a book for a certain age group have to have a particular word count?" "How do I work out who will read my book?" And there’s no easy answer.
You don’t really need to know, of course. Not exactly. When you’re writing to an agent or publisher, a guesstimate will do. Your publisher will fine tune it long before the marketing starts, and they’ll work out how to pitch your book to booksellers. But where do you get your guesstimate?
Unfortunately, there isn’t a set of guidelines for this one, a list of boxes to check, to add up and work out that yes, your book definitely falls into the Young Adult section and will probably appeal to readers aged 14-16. You can’t even base it on characters, content and word count; there are basic commonalities in these areas in different genres, but these are generalisations at best. True, children’s books are a bit shorter, and fantasy novels tend to be on the hefty side. Teenagers like books with teen-aged characters, dealing with teenage issues. But it’s like saying women like books with content about women. Sure, sometimes they do, but they also like crime novels, and science fiction. Classifications can help, but there’s always exceptions.
One of the best ways to figure it out is to read other books like yours. Other authors are your competition; you should be tracking them anyway. If your book is a crime novel with an embittered, male detective with an ex-wife, who’s currently hot on the trail of a serial killer, check out other authors who write books like this. If you’re writing a quest novel with a motley group of travellers who are trying to destroy or find a magical artefact, and the whole thing finishes up with a couple of epic battles in which good prevails, first read Tolkien. Then, use the internet to find other authors who’ve written in a similar style. Read their books, of course, but also go online and look at their websites. Google the book, and see what happens. Check out Amazon, and look at the reader reviews. The ‘People who liked this book also liked…" thingy Amazon does will also help you find other books with the same readership.
If you’re writing to an agent or publisher, this should be enough. "My book is a [insert genre here] novel in a similar vein to This Book by this author, and This Other Book by This Other Author." They’ll get what you’re aiming for, and they’ll be able to deduce the readership you’re targeting. Of course, if they then read your sample and decide you’ve got it totally wrong, that’s another matter. They might be able to pitch it anyway, or they might knock you back. If it’s the latter, maybe you need to go out and read some more.